With the rapid development in wearable medical equipment industry and transparent electronic equipment industry, more and more researchers pay attention to the flexible transparent circuit. The breakthrough of the material and method for flexible transparent circuit is of great significance to the aforementioned two industries. At present, there is a limited number of reports relating to the flexible transparent circuit, among which the most common material is the graphene. However, the transparent circuit made of the graphene has the following disadvantages:
1. The graphene films, especially the graphene films having a large area, tend to form wrinkles;
2. The precise control of the quality for the graphene films is difficult to proceed, and the films get broken easily;
3. The mass production of the graphene films is hard to carry out;
4. The best graphene film has a sheet resistance of around 100 Ohms, and the transparency thereof is only 90%.
Recently, researchers employed the surface patterning method of using nanoparticles to manufacture the flexible transparent circuit. However, such method has a complicated process and an inaccurate circuit control. And the circuit cannot have a good conductivity, transparency and flexibility at the same time, therefore limiting application of the method.
Chinese patent CN101505575A discloses a manufacturing method of a flexible circuit based on PDMS biological compatibility. Although the PDMS substrate disclosed in the patent is transparent, the circuit part of the liquid metal tin-indium-gallium alloy is opaque. Namely, the manufactured circuit comprises a transparent substrate and an opaque conductive material. Meanwhile, the conductive part in the flexible circuit is the liquid metal, and the area where the liquid metal contacts with the conductive devices or the wires is prone to liquid leakage. The insertion or the withdrawal cannot be performed according to actual requirements, otherwise the circuit may fail. As the conductive part of the flexible circuit is the liquid metal, another one sheet must cover the substrate having a channel so that the sheet and the substrate can form a complete and closed channel which is capable of maintaining the conductive metal liquid in the channel. Therefore the requirement for channel sealing is quite high. With a poor sealing, the liquid metal tends to leakage resulting in a short circuit.